U.S. patent number 9,621,079 [Application Number 14/879,243] was granted by the patent office on 2017-04-11 for construction machine.
This patent grant is currently assigned to HITACHI CONSTRUCTION MACHINERY CO., LTD.. The grantee listed for this patent is HITACHI CONSTRUCTION MACHINERY CO., LTD.. Invention is credited to Yuichiro Morita, Takashi Ogawa, Kohei Sakurai.
United States Patent |
9,621,079 |
Ogawa , et al. |
April 11, 2017 |
Construction machine
Abstract
A construction machine includes: a swing structure; an electric
motor that drives the swing structure; an operating device that
outputs an operating signal according to an operating amount and an
operating direction; an inverter device that controls the electric
motor based on a control signal generated based on the operating
signal; a position sensor that detects an actual speed of the
electric motor; and a second controller that determines whether at
least one of a first condition and a second condition is satisfied.
The first condition is satisfied when a sign of a value computed by
subtracting the actual speed from a target speed of the electric
motor that defined by the control signal; and the second condition
is satisfied when a difference between the target speed and the
actual speed is greater than a first reference value, and when the
acceleration is greater than a second reference value.
Inventors: |
Ogawa; Takashi (Tokyo,
JP), Sakurai; Kohei (Tokyo, JP), Morita;
Yuichiro (Hitachi, JP) |
Applicant: |
Name |
City |
State |
Country |
Type |
HITACHI CONSTRUCTION MACHINERY CO., LTD. |
Tokyo |
N/A |
JP |
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Assignee: |
HITACHI CONSTRUCTION MACHINERY CO.,
LTD. (Tokyo, JP)
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Family
ID: |
47295979 |
Appl.
No.: |
14/879,243 |
Filed: |
October 9, 2015 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20160036358 A1 |
Feb 4, 2016 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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14122250 |
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PCT/JP2012/063989 |
May 30, 2012 |
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Foreign Application Priority Data
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Jun 10, 2011 [JP] |
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2011-130630 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
E02F
9/128 (20130101); E02F 9/267 (20130101); H02P
3/18 (20130101); G01P 3/44 (20130101); E02F
9/2095 (20130101); H02P 3/04 (20130101); H02P
6/12 (20130101); H02P 6/06 (20130101); H02P
29/0241 (20160201); Y02T 10/642 (20130101); B60L
2200/40 (20130101); Y02T 10/64 (20130101) |
Current International
Class: |
H02P
6/06 (20060101); H02P 6/12 (20060101); H02P
3/04 (20060101); E02F 9/20 (20060101); G01P
3/44 (20060101); E02F 9/12 (20060101); E02F
9/26 (20060101); H02P 29/024 (20160101); H02P
3/18 (20060101) |
Field of
Search: |
;318/721,720,703,700,490,461,445 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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2007-228721 |
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Sep 2007 |
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JP |
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2010-106511 |
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May 2010 |
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JP |
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2011-26948 |
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Feb 2011 |
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JP |
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1781393 |
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Dec 1992 |
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SU |
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WO 2011099133 |
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Aug 2011 |
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WO |
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Other References
Machine translation JP 2007228721 A. cited by applicant.
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Primary Examiner: Chan; Kawing
Attorney, Agent or Firm: Baker Botts L.L.P.
Parent Case Text
CROSS REFERENCE TO PRIOR APPLICATIONS
This application is a continuation of, and claims the benefit of
priority to, U.S. patent application Ser. No. 14/122,250, filed on
Nov. 26, 2013, which, under 35 U.S.C. .sctn.371, is a U.S. National
Stage entry of International Application No. PCT/JP2012/063989,
which was filed on May 30, 2012, and which claims the benefit of
priority to Japanese Patent Application No. 2011-130630, filed on
Jun. 10, 2011. The International Application was published in
Japanese on Dec. 13, 2012 as WO 2012/169413 A1 under PCT Article
21(2). The contents of the above applications are hereby
incorporated by reference.
Claims
The invention claimed is:
1. A construction machine comprising: a swing structure; an
electric motor that swingably drives the swing structure; an
operating device that outputs operating signals for instructing the
swing structure to swing in a clockwise direction or a
counterclockwise direction and stop according to an operating
amount and an operating direction; and a control device configured
to calculate a target speed of the electric motor from an actual
speed of the electric motor and the operating signal output from
the operating device, and to control the electric motor based on a
control signal generated based on the target speed, wherein the
control device determines whether a sign of a value computed by
subtracting the actual speed from a target speed of the electric
motor, a target speed defined by the control signal, is different
from a sign of acceleration of the electric motor, and determines a
fault occurred in an electronic control system relating to the
electric motor based on the determination result regarding the
signs; a braking device that brakes the electric motor based on a
braking signal, wherein the control device outputs the braking
signal to the braking device when the sign of a value computed by
subtracting the actual speed from the target speed of the electric
motor is different from the sign of acceleration of the electric
motor.
2. The construction machine according to claim 1, further
comprising: an annunciating device that annunciates occurrence of a
fault in the construction machine based on an annunciation signal,
wherein the control device outputs the annunciation signal to the
annunciating device when the sign of a value computed by
subtracting the actual speed from the target speed of the electric
motor is different from the sign of acceleration of the electric
motor.
3. The construction machine according to claim 1, further
comprising: acceleration detecting means that detects acceleration
of the electric motor.
4. The construction machine according to claim 1, wherein the
acceleration of the electric motor is calculated based on target
torque of the electric motor defined by the control signal or
actual torque generated by the electric motor.
5. The construction machine according to claim 1, further
comprising: another control device configure to determine whether
the sign of a value computed by subtracting the actual speed from
the target speed of the electric motor is different from the sign
of acceleration of the electric motor, and to determine a fault
occurred in the electronic control system relating to the electric
motor based on the determination result regarding the signs.
Description
TECHNICAL FIELD
The present invention relates to a construction machine including
an electric motor for driving a swing structure.
BACKGROUND ART
In recent years, more and more construction machines are
electrified with the aim of, for example, improved engine fuel
efficiency and reduced amounts of exhaust gases based on the
techniques relating to hydraulic excavators. Examples of such
construction machines include a hybrid construction machine that
incorporates both a hydraulic actuator and an electric motor as
actuators for driving different parts of the machine, in addition
to an engine and an electric motor (a generator motor) as prime
movers for a hydraulic pump. A known hybrid construction machine
drives hydraulic actuators (hydraulic cylinders and hydraulic
motors) to cause a work implement to perform work and a track
structure to perform a traveling operation. It also drives an
electric motor to cause a swing structure (e.g., an upper swing
structure in a hydraulic excavator) to perform a swing
operation.
The hybrid construction machine of the foregoing type may use a
controller (e.g., an inverter device) for controlling the electric
motor to achieve intended swing control by converting an operation
amount of a swing operating lever operated by an operator to a
corresponding electric signal and applying the electric signal to
the controller. A fault that may occur in an electronic control
system that includes a sensor for detecting a state of the electric
motor (e.g., a magnetic pole position sensor of the electric
motor), the controller, and the electric motor in a series of
control processes, however, hampers correct swing control,
resulting in a swing operation not intended by the operator being
performed.
A known technique for avoiding such a situation as that described
above uses a controller that monitors a difference between a speed
command of an electric motor (a target speed) generated based on
the operation amount of the swing operating lever and an actual
speed of the electric motor and determines the operation to be a
faulty operation when the difference falls outside a permissible
range (see JP-A-2007-228721).
PRIOR ART DOCUMENT
Patent Document
Patent Document 1: JP-2007-228721-A
SUMMARY OF THE INVENTION
Problem to be Solved by the Invention
In a construction machine including a swing structure that has a
large inertia, however, the speed command often differs widely from
the actual speed. Use of only the magnitude of the difference
between the speed command and the actual speed to determine whether
a faulty operation occurs, as in the abovementioned related art,
can cause inconveniences. Specifically, if the permissible range of
the difference is set to be excessively small, a normal operation
may be erroneously determined to be a faulty one, which may reduce
work efficiency. By contrast, with a permissible range set to be
excessively large, the controller can fail to detect a faulty
operation, resulting in reduced reliability.
The present invention has been made in view of the foregoing
situation and it is an object of the present invention to provide a
construction machine that can prevent erroneous determination and
failure of detection relating to determination of faults in an
electronic control system.
Means for Solving the Problem
To achieve the foregoing object, an aspect of the present invention
provides a construction machine comprising: a swing structure; an
electric motor that drives the swing structure; an operating device
that outputs an operating signal for operating the electric motor
according to an operating amount and an operating direction; first
control means that controls the electric motor based on a control
signal generated based on the operating signal; detecting means
that detects an actual speed of the electric motor; and second
control means that determines whether at least one of a first
condition and a second condition is satisfied, the first condition
that is satisfied when a sign of a value computed by subtracting
the actual speed from a target speed of the electric motor, the
target speed defined by the control signal, is different from a
sign of acceleration of the electric motor, and the second
condition that is satisfied when a difference value between the
target speed and the actual speed is greater than a first reference
value and when the acceleration is greater than a second reference
value.
Effects of the Invention
In the aspect of the present invention, erroneous determination and
failure of detection relating to determination of faults in an
electronic control system can be prevented and thus work efficiency
and reliability can be enhanced.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an illustration showing an appearance of a hybrid
hydraulic excavator including a construction machine control system
according to an embodiment of the present invention.
FIG. 2 is a configuration diagram showing the construction machine
control system according to the embodiment of the present
invention.
FIG. 3 is a diagram showing an exemplary application of the
construction machine control system according to the embodiment of
the present invention to a specific construction machine.
FIG. 4 is a schematic diagram showing a hardware configuration of
an inverter device 13 and its surrounding components according to
the embodiment of the present invention.
FIG. 5 is a functional block diagram showing a main microprocessor
31 according to the embodiment of the present invention.
FIG. 6 is a block diagram showing a fault determining unit 65
according to the embodiment of the present invention.
FIG. 7A is a graph showing an exemplary relation between a speed
command V* and an actual speed V.
FIG. 7B is a graph showing an exemplary relation between the speed
command V* and the actual speed V.
FIG. 7C is a graph showing an exemplary relation between the speed
command V* and the actual speed V.
FIG. 7D is a graph showing an exemplary relation between the speed
command V* and the actual speed V.
MODES FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with
reference to the accompanying drawings. It is noted that a first
controller, a second controller, a first hydraulic sensor, and a
second hydraulic sensor to be described hereunder may be denoted by
controller 1, controller 2, hydraulic sensor 1, and hydraulic
sensor 2, respectively, in the drawings.
FIG. 1 is an illustration showing an appearance of a hybrid
hydraulic excavator including a construction machine control system
according to the embodiment of the present invention. This
hydraulic excavator shown in the figure includes an articulated
work implement 1A and a vehicle body 1B. The work implement 1A
includes a boom 1a, an arm 1b, and a bucket 1c. The vehicle body 1B
includes an upper swing structure 1d and a lower track structure
1e.
The boom 1a is rotatably supported by the upper swing structure 1d
and driven by a hydraulic cylinder (boom cylinder) 3a. The arm 1b
is rotatably supported by the boom 1a and driven by a hydraulic
cylinder (arm cylinder) 3b. The bucket 1c is rotatably supported by
the arm 1b and driven by a hydraulic cylinder (bucket cylinder) 3c.
The upper swing structure 1d is swingably driven by an electric
motor (swing motor) 16 (see FIG. 3). The lower track structure 1e
is driven by left and right track motors (hydraulic motors) 3e and
3f (see FIG. 3). The hydraulic cylinder 3a, the hydraulic cylinder
3b, the hydraulic cylinder 3c, and the electric motor 16 are
controlled for driving by operating devices 4a and 4b (see FIG. 3)
disposed in a cab of the upper swing structure 1d, the operating
devices 4a, 4b outputting hydraulic operating signals.
FIG. 2 is a configuration diagram showing the construction machine
control system according to the embodiment of the present
invention. The system shown in the figure includes the electric
motor 16, a position sensor (e.g., magnetic pole position sensor)
24, the operating device (swing operating lever) 4b, a first
hydraulic sensor 20, a second hydraulic sensor 21, a first
controller 11, an inverter device (electric power conversion
device) 13, and a swing emergency brake 25. Specifically, the
electric motor 16 drives the upper swing structure 1d. The position
sensor 24 detects a rotational position of the electric motor 16.
The operating device 4b outputs a hydraulic operating signal (pilot
pressure) for a swing motion of the upper swing structure 1d
according to an amount through which the operating device 4b is
operated (operating amount) and a direction in which the operating
device 4b is operated (operating direction). The first hydraulic
sensor 20 and the second hydraulic sensor 21 each detect pressure
corresponding to the hydraulic operating signal output from the
operating device 4b and output an electric operating signal
corresponding to the pressure. The first controller 11 calculates a
target speed V* of the electric motor 16 based on the electric
operating signal output from the first hydraulic sensor 20 and an
actual speed V (that may be calculated, for example, from the
rotational position detected by the position sensor 24) of the
electric motor 16 and outputs a control signal (speed command)
according to the target speed V*. The inverter device 13 controls
the electric motor 16 based on the control signal (speed command)
output from the first controller 11. The swing emergency brake 25
brakes the upper swing structure 1d based on a braking signal
output from the first controller 11 or the inverter device 13.
The inverter device (electric power conversion device) 13 is
connected to an electric energy storage device 15 (see FIG. 3),
such as a battery. Converting direct current (DC) power charged in
the electric energy storage device 15 into alternating current (AC)
power (three-phase AC) through switching, the inverter device 13
supplies the AC power to the electric motor 16 to thereby control
the electric motor 16. The inverter device 13 includes an inverter
circuit, a driver circuit, and a second controller (control
circuit) 22. The inverter circuit includes a switching device
(e.g., an insulated gate bipolar transistor (IGBT)). The driver
circuit controls driving of the inverter circuit. The second
controller 22 outputs a control signal (torque command) to the
driver circuit to thereby control to turn on and off the switching
device in the inverter circuit. It is noted that, in the
accompanying drawings, the inverter circuit and the driver circuit
in the inverter device 13 are denoted by "IGBT" as an exemplary
switching device. Thus, in the following, IGBT 23 represents both
the inverter circuit and the driver circuit.
The first hydraulic sensor 20 and the second hydraulic sensor 21
may be each configured as a set of two hydraulic sensors for
individually detecting a clockwise swing and a counterclockwise
swing of the upper swing structure 1d as will be described later.
FIG. 2, however, simply shows one hydraulic sensor each. In
addition, in the embodiment, the pilot pressure (hydraulic
operating signal) output from the operating device 4b is detected
by the first hydraulic sensors 20 and 21 for conversion into a
corresponding electric signal. An arrangement may nonetheless be
made in which the electric operating signal according to the
operating direction and the operating amount of the operating
device 4b is directly output. In this case, a position sensor that
detects rotational displacement of the operating lever in the
operating device 4b (e.g., a rotary encoder) may be used.
Additionally, in the embodiment, the operating device 4b has two
hydraulic sensors 20 and 21. Sensors operating on different
detection schemes may nonetheless be combined together; for
example, a combination of the hydraulic sensor and the position
sensor. This can enhance reliability of the system.
The electric operating signal output from the first hydraulic
sensor 20 is applied to the first controller 11. The electric
operating signal output from the second hydraulic sensor 21 is
applied to the second controller 22 disposed in the inverter device
13.
The first controller 11 calculates the target speed V* of the
electric motor 16 based on the electric operating signal output
from the first hydraulic sensor 20 and the actual rotational speed
(actual speed V) of the electric motor 16 applied via the second
controller 22. The first controller 11 then outputs a control
signal (speed command) corresponding to the target speed V* to the
second controller 22.
The second controller 22 outputs a torque command (control signal)
generated in consideration of the speed command (control signal)
applied thereto from the first controller 11, a torque limit
defined by, for example, device performance restrictions (e.g.,
pressing force, electricity, DC line voltage), the rotational
position (actual speed V) of the electric motor 16 detected by the
position sensor 24, and a current value (actual current) detected
by a three-phase motor current sensor 30. The second controller 22
then turns on or off the IGBT 23 based on the torque command,
thereby controlling the electric motor 16 (see FIG. 5).
Additionally, the second controller 22 calculates the actual speed
V of the electric motor 16 using the rotational position of the
electric motor 16 detected by the position sensor 24 and outputs
the calculated actual speed V (produces a feedback output) to the
first controller 11.
It is noted that, in the embodiment, the speed command is output as
a command value from the first controller 11; however, a swing
torque command may be used instead. In this case, the second
controller 22 is to produce a feedback output of the actual torque
value of the electric motor 16 to the first controller 11.
A hydraulic brake may, for example, be used for the swing emergency
brake (braking device) 25. The hydraulic brake includes a plurality
of discs pressed by brake shoe springs. The brake is released when
hydraulic pressure for releasing the brake is applied and the
hydraulic pressure overcomes a force of the springs.
FIG. 3 is a diagram showing an exemplary application of the
construction machine control system according to the embodiment of
the present invention to a specific construction machine. In FIG.
3, like or corresponding parts are identified by the same reference
numerals as used in the preceding figures and descriptions for
those parts may not be duplicated (this applies to each of the
subsequent figures).
In FIG. 3, the operating devices 4a and 4b each include an
operating lever and generate a pilot pressure according to the
operating direction and the operating amount of the operating lever
operated by an operator. The pilot pressure is generated by a
primary pressure generated in a pilot pump (not shown) being
reduced to a secondary pressure according to the operating amount
of the operating devices 4a and 4b. The pilot pressure defined
according to the operating amount of the operating device 4a is
sent to a pressure receiving part of each of spool type directional
control valves 5a to 5f. This causes the directional control valves
5a to 5f to change their positions from the neutral positions shown
in the figure. The directional control valves 5a to 5f change the
direction of flow of hydraulic fluid generated from a hydraulic
pump 6 powered by an engine 7 to thereby control driving of
hydraulic actuators 3a to 3f. Should pressure inside a hydraulic
line rise inordinately, the hydraulic fluid is released to a tank 9
via a relief valve 8. The hydraulic actuators 3a to 3c serve as the
hydraulic cylinders that drive the boom 1a, the arm 1b, and the
bucket 1c, respectively. The hydraulic actuators 3e and 3f serve as
hydraulic motors that drive the left and right track devices
disposed at the lower track structure 1e.
A driving power conversion machine (generator motor) 10 is
connected between the hydraulic pump 6 and the engine 7. The
driving power conversion machine 10 functions as both a generator
and a motor. As the generator, the driving power conversion machine
10 converts driving power of the engine 7 to electric energy and
outputs the electric energy to inverter devices 12 and 13. As the
motor, the driving power conversion machine 10 uses electric energy
supplied from the electric energy storage device 15 to assist in
driving the hydraulic pump 6. The inverter device 12 converts
electric energy of the electric energy storage device 15 to AC
electric power and supplies the AC electric power to the driving
power conversion machine 10 to assist in driving the hydraulic pump
6.
The inverter device 13 supplies electric power output from the
driving power conversion machine 10 or the electric energy storage
device 15 to the electric motor 16 and corresponds to the inverter
device 13 shown in FIG. 2. Thus, the inverter device 13 includes
the second controller 22 shown in FIG. 2. With an input of a speed
command (control signal) received from the first controller 11, the
inverter device 13 controls driving of the electric motor 16. The
inverter device 13 also determines whether a fault occurs in an
electronic control system (the electric motor 16, the position
sensor 24, and the inverter device 13) relating to the electric
motor 16 based on the target speed V* defined by the speed command
output from the first controller 11, the actual speed V of the
electric motor 16 calculated from a detected value of the position
sensor 24, and acceleration dV/dt that is a change with time of the
actual speed V of the electric motor 16. The second hydraulic
sensors 21 (21a, 21b) are disposed in, out of pilot lines
connecting between the operating devices 4a and 4b and the
directional control valves 5a to 5f, two pilot lines that control
swing motions of the upper swing structure 1d in clockwise and
counterclockwise directions.
A chopper 14 controls voltage of a DC electric power line L1. The
electric energy storage device 15 supplies electric power to the
inverter devices 12 and 13 via the chopper 14 and stores electric
energy generated by the driving power conversion machine 10 and
electric energy regenerated from the electric motor 16. A
capacitor, a battery, or both may be used for the electric energy
storage device 15.
The first controller 11 calculates the target speed V* of the
electric motor 16 based on electric operating signals input from
the first hydraulic sensors 20 (20a, 20b) connected, respectively,
to, out of the pilot lines connecting between the operating devices
4a and 4b and the directional control valves 5a to 5f, two pilot
lines that control the swing motions of the upper swing structure
1d in the clockwise and counterclockwise directions. The first
controller 11 then outputs a control signal (swing operating
command) according to the calculated target speed V* to the
inverter device 13. Additionally, the first controller 11 performs
driving power regenerative control that recovers electric energy
from the electric motor 16 during swing braking. Furthermore,
during the driving power regenerative control and when excess
electric power is produced under light hydraulic load, the first
controller 11 performs control to store the recovered electric
power and excess electric power in the electric energy storage
device 15.
The inverter devices 12, 13, the chopper 14, and the first
controller 11 transmit and receive signals required for the control
via a communication line L2.
FIG. 4 is a schematic diagram showing a hardware configuration of
the inverter device 13 and its surrounding components according to
the embodiment of the present invention. As shown in FIG. 4, the
second controller 22 includes a main microprocessor (first
microprocessor) 31 and a monitoring microprocessor (second
microprocessor) 32 as control units. The main microprocessor 31 and
the monitoring microprocessor 32 are control units independent of
each other. Communication drivers 33a and 33b are connected to the
main microprocessor 31 and the monitoring microprocessor 32,
respectively, each assuming an interface between the corresponding
microprocessor 31 or 32 and the communication line L2.
The main microprocessor 31 receives inputs of a speed command input
from the first controller 11 via the communication driver 33a, an
electric operating signal output from the second hydraulic sensor
21, rotational position information of the electric motor 16 output
from the position sensor 24, and actual current information output
from the current sensor 30. Using the information from the position
sensor 24 and the current sensor 30, the main microprocessor 31
outputs a gate control signal to the IGBT 23 so as to satisfy the
speed command input from the first controller 11 by way of the
communication line L2.
The monitoring microprocessor 32 receives inputs of a speed command
input from the first controller 11 via the communication driver
33b, an electric operating signal output from the second hydraulic
sensor 21, rotational position information of the electric motor 16
output from the position sensor 24, and current information output
from the current sensor 30. The monitoring microprocessor 32
performs a process of determining whether a fault exists in the
electronic control system relating to the electric motor 16 based
on the target speed V* of the electric motor 16 defined by the
speed command, the actual speed V of the electric motor 16
calculated from the rotational position information from the
position sensor 24, and the acceleration dV/dt that is a change
with time of the actual speed V of the electric motor 16.
FIG. 5 is a functional block diagram showing the main
microprocessor 31 according to the embodiment of the present
invention. As shown in FIG. 5, the main microprocessor 31 includes
a speed control unit 60, a torque control unit 61, a PWM control
unit 62, a speed calculating unit 64, and a fault determining unit
65. The main microprocessor 31 controls the speed of the electric
motor 16 through feedback control.
The speed control unit 60 generates a torque command intended for
the torque control unit 61 so that the actual speed V calculated by
the speed calculating unit 64 follows the speed command (target
speed V*).
The torque control unit 61 generates a voltage command so that
actual torque follows the torque command generated by the speed
control unit 60. In addition, if the electric motor 16 cannot be
made to follow the torque command output from the speed control
unit 60 due to, for example, device performance restrictions
relating to the hydraulic excavator, the torque control unit 61
limits the torque command (specifically, reduces as necessary the
torque command output from the speed control unit 60).
The PWM control unit 62 generates a gate control signal through
pulse width modulation (PWM).
The torque command generated by the speed control unit 60 is
converted to a voltage command based on a correction made by the
torque control unit 61. The voltage command generated by the torque
control unit 61 is output to the PWM control unit 62 and converted
to a gate control signal. The gate control signal generated by the
PWM control unit 62 is output to the IGBT 23. It is noted that, in
this embodiment, torque of the electric motor 16 is controlled by
feedback control that causes the actual current of the current
sensor 30 to follow a current command corresponding to the torque
command.
The speed calculating unit 64 calculates the actual speed V of the
upper swing structure 1d. The speed calculating unit 64 receives an
input of rotational position information (resolver signal) of the
electric motor 16 output from the position sensor 24 and, based on
the rotational position information, calculates the actual speed
V.
The fault determining unit 65 determines whether a fault occurs in
the electronic control system (performs a fault determining
process) using the speed command V* received from the first
controller 11 via the communication driver 33a and the actual speed
V calculated by the speed calculating unit 64. The fault
determining process performed by the fault determining unit 65 will
be described in detail using a relevant figure.
FIG. 6 is a block diagram showing the fault determining unit 65
according to the embodiment of the present invention. As shown in
FIG. 6, the fault determining unit 65 includes an acceleration
calculating unit 82, a backward rotation detecting unit 80, and an
overspeed detecting unit 81.
The acceleration calculating unit 82 receives an input of the
actual speed V calculated by the speed calculating unit 64. The
acceleration calculating unit 82 calculates the acceleration dV/dt
using the actual speed V input thereto and outputs the calculated
acceleration dV/dt to the backward rotation detecting unit 80 and
the overspeed detecting unit 81. It is noted that the embodiment is
configured so that the acceleration dV/dt is calculated from the
actual speed V when the acceleration of the electric motor 16 is
calculated. The acceleration dV/dt may nonetheless be calculated
from the torque command (target torque) output from the electric
motor 16 or the actual torque generated by the electric motor 16
(that is calculated from the output of the current sensor 30).
Alternatively, instead of the foregoing, an acceleration detector,
such as acceleration sensors and gyro sensors, may be installed and
the output from the acceleration detector is used.
The backward rotation detecting unit 80 receives inputs of a speed
command (target speed V*) output from the first controller 11, the
actual speed V calculated by the speed calculating unit 64, and the
acceleration dV/dt calculated by the acceleration calculating unit
82. The backward rotation detecting unit 80 determines whether a
condition (a first condition) is satisfied or not, which is
satisfied when a sign of a value computed by subtracting the actual
speed V from the target speed V* (value of a difference in speed)
is different from a sign of the acceleration dV/dt. Based on this
determination, the backward rotation detecting unit 80 determines
whether the electric motor 16 rotates backward as against an
instruction of the operator. The example shown in the figure
represents a case in which the sign of the value of the target
speed V* from which the actual speed V is subtracted is detected to
be "positive" and the sign of the acceleration dV/dt is detected to
be "negative."
The overspeed detecting unit 81 receives inputs of a speed command
(target speed V*) output from the first controller 11, the actual
speed V calculated by the speed calculating unit 64, and the
acceleration dV/dt calculated by the acceleration calculating unit
82. The overspeed detecting unit 81 determines whether a condition
(a second condition) is satisfied or not, which is satisfied when a
difference value between the target speed V* and the actual speed V
is greater than a reference value Vth (a first reference value) and
when the acceleration is greater than a reference value .beta.th (a
second reference value). Based on this determination, the overspeed
detecting unit 81 determines whether the rotational speed of the
electric motor 16 is excessively high as against an instruction of
the operator. Considering the magnitude of the acceleration in
addition to the magnitude of the speed difference enables the
following determination to be made: specifically, when the
acceleration is smaller than the second reference value .beta.th
even with the speed difference being so considerable as to exceed
the first reference value Vth, the considerable speed difference is
attributable to inertia of the upper swing structure 1d and the
condition can be determined to be normal. Thus, the inertia of the
upper swing structure 1d can be taken into consideration, so that
the likelihood of occurrence of erroneous determination and failure
of detection can be reduced as compared with a case in which focus
is placed only on the speed difference.
If at least one of the first condition and the second condition is
satisfied in the backward rotation detecting unit 80 or the
overspeed detecting unit 81, the fault determining unit 65
determines that a fault (e.g., a faulty IGBT 23 or electric motor
16, or a fault in parts other than the swing control system) has
occurred in the electronic control system relating to the electric
motor 16. The fault determining unit 65 according to the
embodiment, upon determining that a fault has occurred as described
above, outputs a gate off signal to the IGBT 23 to set the electric
motor 16 in a free run state before outputting a braking signal to
the swing emergency brake 25 to brake the electric motor 16.
Operating the swing emergency brake 25 as described above allows
the electric motor 16 to be braked even when the braking cannot be
applied through a control approach by outputting a zero speed
command to the inverter device 13 (specifically, causing the
inverter device 13 to apply a voltage that results in the electric
motor 16 generating deceleration torque).
An arrangement may even be made in which an annunciating device
that annunciates occurrence of a fault in the hydraulic excavator
based on an annunciation signal is connected to the fault
determining unit 65; when at least one of the first condition and
the second condition is satisfied, as in the above-described case,
an annunciation signal instead of, or together with, the braking
signal is output to the annunciating device, so that the operator
or a supervisor may be advised that a fault has occurred.
Nonlimiting examples of the annunciating device include a display
device 26 (see FIG. 2) disposed near a operator's seat in the cabin
in the hydraulic excavator, a warning light, and an alarm. In this
case, the display device 26 may display a message prompting
inspection or repair of devices, in addition to the message
indicating that a fault has occurred.
The fault determining process performed in the hydraulic excavator
having the arrangements as described above will be exemplarily
described below. FIGS. 7A, 7B, 7C, and 7D are graphs showing
exemplary relations between the speed command V* and the actual
speed V. Of these, FIGS. 7A and 7B show operations from stop to
swing. In FIG. 7A, the electric motor 16 is accelerated normally;
and neither the first condition nor the second condition is
satisfied, so that the fault determining unit 65 does not determine
a fault. FIG. 7B shows a case in which the electric motor 16
rotates backward against the intention of the operator. In this
case, the sign of the value of the target speed V* from which the
actual speed V is subtracted is "positive" and the sign of the
acceleration dV/dt is "negative." Thus, at least the first
condition is satisfied and a fault can be determined to have
occurred, so that the fault determining unit 65 outputs a braking
signal to the swing emergency brake 25.
FIGS. 7C and 7D show operations from swing to stop. In FIG. 7C, the
operator places the operating lever of the operating device 4b back
in the neutral position to make the speed command zero, thereby
bringing the upper swing structure 1d to a stop. In this case, the
electric motor 16 is decelerated normally; and neither the first
condition nor the second condition is satisfied, so that the fault
determining unit 65 does not determine a fault. FIG. 7D shows an
operation in which the operator operates the lever in a backward
rotation direction to thereby bring the upper swing structure 1d to
a stop. In this case, the speed command and the actual speed are
reverse in polarity and a condition in which the speed difference
is excessively great continues to exist; however, the operation is
still normal. In this case, the sign of the value of the target
speed V* from which the actual speed V is subtracted is "negative"
and the sign of the acceleration dV/dt is also "negative." Thus,
the first condition is not satisfied. While the difference between
the target speed V* and the actual speed V is greater than the
first reference value Vth, the acceleration dV/dt is smaller than
the second reference value .beta.th as in the case of FIG. 7C
depicting a normal condition, so that the second condition is not
satisfied, either. Thus, the embodiment can determine such a case
to be normal without making any false determination.
In the hydraulic excavator having the arrangements as described
above, erroneous determination relating to the determination of
faults in the electronic control system can be prevented, which
improves availability of the hydraulic excavator and work
efficiency. Additionally, failure of detection relating to the
determination of faults can also be prevented, which improves
reliability.
In the above-described embodiment, the fault determining process is
performed by using the speed (the speed command V* and the actual
speed V) of the electric motor 16. A process similar to that
mentioned above can also be performed by using torque of the
electric motor 16 (the torque command output from the speed control
unit 60 and the actual torque calculated from the output of the
current sensor 30). Determination accuracy tends to be reduced with
a considerable difference between the speed command V* and the
actual speed V. The performance of the fault determining process
based on the torque as described above can, however, prevent the
determination accuracy from being reduced.
The above embodiment has been described for a case in which the
fault determining process is performed in the main microprocessor
31. The speed calculating unit 64 and the fault determining unit 65
may nonetheless be mounted on the monitoring microprocessor 32 to
enable the monitoring microprocessor 32 to perform the similar
fault determining process function. Similarly to the main
microprocessor 31, the monitoring microprocessor 32 receives the
speed command V* from the communication line L2 and inputs of
signals from the position sensor 24 and the current sensor 30.
Thus, the fault determining process described with reference to
FIG. 6 may be performed using the pieces of information mentioned
above and the speed calculating unit 64 and the fault determining
unit 65. When a fault is detected, the monitoring microprocessor 32
outputs a gate off signal to the IGBT 32 and a braking signal to
the swing emergency brake 25. This enables the monitoring
microprocessor 32 to stop the swing motion of the upper swing
structure 1d, even if, for example, a fault occurs in the main
microprocessor 31 and illegal motor control is performed. It is
noted that the monitoring microprocessor 32 does not need to
perform the motor control and is thus not required to offer
calculation performance as high as that of the main microprocessor
31, so that an inexpensive microprocessor may be used for the
monitoring microprocessor 32. Understandably, the monitoring
microprocessor 32 may be omitted, if the motor control and the
fault determining process are performed only by the main
microprocessor 31 as in the above-described embodiment.
Another possible arrangement for monitoring the status of the main
microprocessor 31 is, in addition to causing the monitoring
microprocessor 32 to perform the above process with the monitoring
microprocessor 32 and the main microprocessor 31 connected to each
other so as to permit communications therebetween, to combine with
the foregoing an example calculation system in which the monitoring
microprocessor 32 sets an appropriate problem to the main
microprocessor 31 and, based on the answer to the problem from the
main microprocessor 31, diagnoses the main microprocessor 31. An
exemplary method of this kind is to cause the main microprocessor
31 to perform an arithmetic operation at appropriate intervals and
the monitoring microprocessor 32 determines whether a result of the
operation is right or wrong to thereby diagnose the status of the
main microprocessor 31.
Additionally, the above embodiment has been described for a case in
which the communication driver 33b is mounted so as to allow the
monitoring microprocessor 32 to perform a communication function
and to receive the speed command V* directly from the first
controller 11. The use of the communication driver 33b can,
however, be omitted, if the speed command V* is to be received by
way of the main microprocessor 31, which allows the system to be
configured at lower cost. In a configuration such as that described
above, preferably, the first controller 11 transmits the speed
command V* with a check code or a serial number appended to it in
advance, in order to prevent a situation from occurring in which
the monitoring microprocessor 32 receives a false command value
when the main microprocessor 31 is faulty and is thus unable to
detect the fault in the main microprocessor 31. If the main
microprocessor 31 transmits the data directly without its being
processed to the monitoring microprocessor 32, the monitoring
microprocessor 32 can determine that the command value has not been
falsified due to a fault in the main microprocessor 31.
Fault detection of the first controller 11 and the second
controller 22 can be achieved by mutual monitoring by the first
controller 11 and the second controller 22, in addition to the
embodiment described above. Specific examples of mutual monitoring
by the first controller 11 and the second controller 22 include the
example calculation system described earlier and checking that an
alive counter (a counter that is incremented at every communication
cycle and reset when a predetermined value is reached) is
updated.
The arrangements of the hydraulic excavator as those described
above can achieve safety of the electronic control system relating
to the upper swing structure 1d at low cost without permitting
redundancy in each of the controllers, even when any of the
position sensor 24, the controllers 11, 12, the inverter device 13,
and the electric motor 16 is faulty. In addition, the output from
the second hydraulic sensor 21 as one of the redundant hydraulic
sensors is applied to the inverter device 13. This achieves another
effect of the present invention to improve availability of the
hydraulic excavator, because a swing motion can continue even when
the first controller 11 that calculates the swing command or the
communication line L2 between the first controller 11 and the
inverter device 13 is faulty.
The embodiment described above incorporates a crawler type
hydraulic excavator as an example of the construction machine. The
present invention is nonetheless similarly applicable to any other
type of construction machine that includes an upper swing structure
swingably driven an electric motor (e.g., a wheel type hydraulic
excavator and a crawler type or wheel type crane).
DESCRIPTION OF REFERENCE NUMERALS
1A Front implement 1B Vehicle body 1a Boom 1b Arm 1c Bucket 1d
Upper swing structure 1e Lower track structure 3a Boom cylinder 3b
Arm cylinder 3c Bucket cylinder 3e Left-side track motor 3f
Right-side track motor 4a, 4b Operating device 5a to 5f Spool type
directional control valve 6 Hydraulic pump 7 Engine 8 Relief valve
9 Hydraulic fluid tank 10 Driving power conversion machine 11 First
controller 12, 13 Inverter device 14 Chopper 15 Electric energy
storage device 16 Electric motor (swing motor) 20 First hydraulic
sensor 20a First hydraulic sensor (left side) 20b First hydraulic
sensor (right side) 21 Second hydraulic sensor 21a Second hydraulic
sensor (left side) 21b Second hydraulic sensor (right side) 22
Second controller 23 IGBT (inverter circuit) 24 Position sensor 25
Swing emergency brake 26 Display device 30 Current sensor 31 Main
microprocessor 32 Monitoring microprocessor 33a, 33b Communication
driver 60 Speed control unit 61 Torque control unit 64 Speed
calculating unit 65 Fault determining unit 80 Backward rotation
detecting unit 81 Overspeed detecting unit 82 Acceleration
calculating unit L1 DC electric power line L2 Communication
line
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